Cacher is the code snippet organizer for pro developers

What's wrong?

const a = [1, 2]
[...a].map((a, b) => a + b);

foo = () => {
    return
    {
        bar: 1
    }
}
foo()

Arguments

(() => {
    var foo = { foo: 1 };
    var bar = 2;
    var tar = new Number(3);
    console.log(JSON.stringify({foo, bar, tar}));
    moo(foo, bar, tar);
    console.log(JSON.stringify({foo, bar, tar}));
    
    function moo(a, b = 4, c) {
        a.foo++;
        b = 5;
        c--;
        console.log(`new Number(${c}) === ${c}`, (new Number(c) === c), typeof new Number(c), typeof (c))
        console.log(JSON.stringify({ a, b, c }));
    }
})();

Tasks:

[1, 2, 3, 4].duplicate() // [1,2,3,4,1,2,3,4]

fetchUrl('https://ya/ru')
    .then(t => console.log("then: ", t))
    .catch(e => console.log("catch: ", e))

// сatch должен сработать только после 7 неудачных попыток получить содержимое страницы внутри fetchUrl

// Внутри fetchUrl можно использовать условный метод fetch()
// для реализации нужно испольовать промисы

More at https://www.youtube.com/watch?v=2pL28CcEijU

Number.MAX_VALUE > 0;
Number.MIN_VALUE < 0;

1 < 2 < 3;
3 > 2 > 1;

42.toFixed(2);
42. toFixed(2);
42 .toFixed(2);
42 . toFixed(2);
42.0.toFixed(2);
42..toFixed(2);

[] == ![];
[] + {};
{} + [];

Number("");
Number(" ");
Number("\r\n\t");

Number("0");
Number("-0");
JSON.parse("-0");

- 0;
Number("- 0")

JSON.stringify(-0);
String(-0);
-0 + "";

Number("0.");
Number(".0");
Number(".");

Number(undefined);
Number(null);

Number("0O10");
Number("0X10");
Number("2O17");

Number({});
Number([]);

String({});
String([]);

String(null);
String([null]);

String(undefined);
String([undefined]);

String([null,null,]);
String([undefined,undefined,]);
String([,,]);

''``

/,/.test([,])
/,/.test([1,])
/,/.test([1,2])

Array(3);
[,,,]

a = [];
a.length = 3;
a;

[undefined,undefined,undefined]

[1,100000,30,21,4].sort()

let cats = [];
cats[30] = 'Dusty';
cats['foo'] = 'Bar';
cats.length; // ?
Object.keys(cats).length; // ?

Array(3).join("a");
Array(3).map(x => "a");

Array.apply(null, {length: 3})
Array.apply(null, [3])
Array.apply(null, Array(3))
Array.apply(null, [,,,])
Array.apply(null, () => {})
Array.call(null, 3)

'👨‍👩‍👧‍👦'.slice(2)

'💩💩💩'.split('')
[...'💩💩💩']
[...'👨‍👩‍👧‍👦']

o1 = {foo:1};

o2 = Object.create(null);
o2.foo = 1;

o1 + "";
o2 + "";

let a = 42;
switch (a) {
    default:
        a += 1;
    case 44:
        a += 2;
    case 45:
        a += 5;
        break;
    case 46:
        a += 9;
        break;
}

(() => {
    try {
        return 2;
    }
    finally {
        return 3;
    }
})();

(() => {
    try {
        return 2;
    }
    finally {
        // return 3;
    }
})();

(o => o)();
(() => {})();
(() => {return;})();
(() => undefined)();
(() => {return undefined})();

function *foo(){
  try {
    yeld 1;
    yeld 2;
  }
  finally {
    yeld 'finally';
  }
  yeld '?';
}
let it = foo();
it.next();
it.return();
it.next();

function *foo(){
    yeld 1;
    yeld 2;
    return 3;
}
for (let i of foo()) {
    console.log(i);
}

typeof a;
typeof b;
let b;

foo = (x = {y: 10}, {y = 20} = {})  => console.log(x.y, y);
foo();
foo({},{});
foo({y:30},{y40});

class Px {
  foo() { console.log('Px:foo'); }
}

class Cx extends Px {
  bar() { console.log('Cx:bar'); }
  foo() { this.bar(); super.foo(); }
}
class Py {
  foo() { console.log('Py:foo'); }
}
class Cy extends Px {
  bar() { console.log('Cy:bar'); }
  foo() { this.bar(); super.foo(); }
}

let x = new Cx();
let y = new Cy();

x.foo();
y.foo();

y.foo.call(x);

const obj = {
    foo: 1,
    bar: {
        tar: true
    }
}
Object.freeze(obj)
obj.foo = 2
obj.bar.tar = false
console.log(obj)

0 || 1
0 ?? 1
'' || 1
'' ?? 1
null || 1
null ?? 1

null > 0
null >= 0
null == 0